Early closing miller cycle internal combustion engine

ABSTRACT

The present invention mitigates restriction due to the fact that the opening period (angular working range) of the intake valve becomes smaller in the early closing Miller cycle operation, in which the intake valve closing timing occurs before the bottom dead center. The crankshaft center O 1  is offset on one side from the cylinder central axis X. The top dead center and the bottom dead center of the piston occur when the three points, namely the crankshaft center O 1 , the crankpin center O 2 , and the piston pin center O 3  are aligned in one line. At this time, the connecting rod and the crank arm are inclined relative to the axis X. The inclination angle θ bdc  at the bottom dead center is greater than the inclination angle θ tdc  at the top dead center. Therefore, as the crankshaft rotates in the direction of arrow ω, the intake process and the expansion process become greater than 180° CA, while the compression process and the exhaust process become smaller than 180° crank angle. Accordingly, the angular working range of the intake valve is enlarged. Therefore, the restriction to the valve lift curve is mitigated.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an early closingMiller cycle internal combustion engine. More specifically, the presentinvention relates an early closing Miller cycle internal combustionengine, in which Miller cycle is achieved by advancing the angulartiming of the closing of an intake valve relative to the intake bottomdead center.

[0003] 2. Background Information

[0004] A Miller cycle internal combustion engine has a greater expansionrate than compression rate in order to improve the fuel consumptionrate. Thus, the Miller cycle internal combustion engine has recentlybeen drawing more interest in the automotive field. Miller cycleinternal combustion engines are broadly divided into late closing Millercycle engines and early closing Miller cycle engines. In the lateclosing Miller cycle engines, the intake valve closing timing is delayedrelative to the intake bottom dead center, such that the air that hasbeen inhaled is partially pushed back. In the early closing Miller cycleengines, the intake valve closing timing is advanced relative to theintake bottom dead center, such that the intake process is effectivelyshortened. An early closing Miller cycle engine is disclosed in JapaneseLaid-Open Patent H7-310565.

[0005] Typically, the intake valve of an internal combustion engine ismechanically driven via a camshaft. However, there various types ofvalve activation devices have been suggested, in which anelectromagnetic actuator is provided in each intake valve. In such case,each valve can be opened and closed separately. Also, there is moreflexibility in the control of the opening and closing timings. An valveactivation device is disclosed in Japanese Laid-Open Patent ApplicationH8-189315.

[0006] In view of the above, there exists a need for an early closingMiller cycle engine which overcomes the problems in the prior art. Thisinvention addresses this need in the prior art as well as other needs,which will become apparent to those skilled in the art from thisdisclosure.

SUMMARY OF THE INVENTION

[0007] In an early closing Miller cycle engine, since the intake valveclosing timing is before the intake bottom dead center, as long as theintake valve opening timing is set at an appropriate position from thepoint of view of valve overlap, the intake valve opening period (or thevalve angular working range) becomes very short. Accordingly, the intakevalve has to be opened and closed abruptly. As a result, an impact dueto momentum of the valve becomes large. Therefore, the durability of thevalve is likely to decrease. Also, the valve lift curve has to bedesigned such that the valve does not fall out of the valve lift curvein the high-speed region. As a result, flexibility of the valve designdecreases.

[0008] It has been discovered that it is possible to use a movable valvemechanism that utilizes an electromagnetic or hydraulic actuator tooperate an engine in a Miller cycle only under certain conditions. Insuch valve driving device that does not depend on a crankshaft, theminimum length of the valve opening period is uniquely determined basedon the responsiveness of the actuator or the applied voltage, regardlessof the rotations of the mechanism. Therefore, when early closed Millercycle engine is combined with this type of valve driving device, it isdifficult to adjust the valve timing in the high-speed region, in whichthe actual period of time that corresponds to the valve opening periodbecomes shorter. In other words, operation in high-rotation region ofthe engine in a Miller cycle is restricted. Otherwise, a larger actuatorwill be necessary, or more electric power will be necessary to furtherincrease the responsiveness.

[0009] On the other hand, with regard to a late closing Miller cycleengine, in which the intake valve closing timing is delayed until afterthe bottom dead center, the valve opening period is longer than that ofa regular Otto cycle engine. Therefore, such problem does not occur.

[0010] In accordance with one aspect of the present invention, an earlyclosing Miller cycle internal combustion engine is provided. The earlyclosing Miller cycle internal combustion engine comprises a pistonslidably disposed in a cylinder to reciprocate along a cylinder centralaxis, an intake valve disposed in an intake opening of the cylinder toopen and close the intake opening, an exhaust valve disposed in anexhaust opening of the cylinder to open and close the exhaust opening, amovable valve mechanism arranged to close the intake valve before abottom dead center to achieve the Miller cycle operation, a crankshaftoperatively coupled to the piston to move the piston in the cylinder,the crankshaft having a crankshaft center axis of rotation offset fromthe cylinder central axis in such a direction that an intake process andan expansion process have greater than 180° crank angle.

[0011] These and other objects, features, aspects and advantages of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which, taken in conjunction with theannexed drawings, discloses a preferred embodiment of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Referring now to the attached drawings which form a part of thisoriginal disclosure:

[0013]FIG. 1 is a diagrammatic structural view of an early closingMiller cycle internal combustion engine in accordance with the presentinvention;

[0014]FIG. 2 is a characteristics graph showing the valve liftcharacteristics of intake valve in accordance with the presentembodiment; and

[0015]FIG. 3 is a diagrammatic view of a crankshaft having a connectingrod and piston coupled thereto at top dead center, wherein thecrankshaft center is offset from the from the piston pin center inaccordance with the present invention;

[0016]FIG. 4 is a diagrammatic view of a crankshaft having a connectingrod and piston coupled thereto at bottom dead center, wherein thecrankshaft center is offset from the from the piston pin center inaccordance with the present invention;

[0017]FIG. 5 is a diagrammatic view of a crankshaft having a connectingrod and piston coupled thereto at top dead center, wherein thecrankshaft center is aligned with the piston pin center;

[0018]FIG. 6 is a diagrammatic view of a crankshaft having a connectingrod and piston coupled thereto at bottom dead center, wherein thecrankshaft center is aligned with the piston pin center;

[0019]FIG. 7 is a valve timing diagram showing opening and closingtimings of the intake valve during an early closing Miller cycleoperation, where the crank offset is zero such as shown in FIGS. 5 and6;

[0020]FIG. 8 is a valve timing diagram showing opening and closingtimings of the intake valve during early closing Miller cycle operationin the case of the present invention, where the crankshaft center isoffset from the from the piston pin center such as shown in FIGS. 3 and4;

[0021]FIG. 9 is a diagrammatic structural view of an alternateembodiment of the present invention in which a hydraulic valve drivingdevice is used; and

[0022]FIG. 10 is a diagrammatic structural view of an early closingMiller cycle internal combustion engine in accordance with anotherembodiment of the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Selected embodiments of the present invention will now beexplained with reference to the drawings. It will be apparent to thoseskilled in the art from this disclosure that the following descriptionof the embodiments of the present invention is provided for illustrationonly, and not for the purpose of limiting the invention as defined bythe appended claims and their equivalents.

[0024] Referring initially to FIG. 1, an early closing Miller cycleinternal combustion engine is diagrammatically illustrated to explain afirst embodiment of the present invention. Basically, the early closingMiller cycle internal combustion engine embodiment of the presentinvention has an engine control unit 1 that controls an electromagneticactuator controller 6 to open and close a plurality of intake valves 17(only one shown) and a plurality of exhaust valve 19 (only one shown) byan intake valve driving actuator 16 and an exhaust valve drivingactuator 18, respectively, such that the valves 17 and 19 independentlyopen and close intake openings 17 a and exhaust openings 19 a.

[0025] In the present invention, “Miller cycle internal combustionengine” is not limited to internal combustion engines that alwaysoperate as a Miller cycle internal combustion engine. It also includesinternal combustion engines that operate as a Miller cycle internalcombustion engine only under certain operative circumstances by varyingthe closing period of the intake valves 17 through the use of a movablevalve device. In this case, a target closure timing of the intake valves17 are calculated in accordance with one or more engine operatingconditions, and the movable valve device is controlled so that theclosure timing of the intake valves 17 meets the calculated targetclosure timing. The target closure timing includes at least a timing setbefore the bottom dead center.

[0026] As seen in FIG. 1, a piston 13 is slidably disposed within acylinder 12. Of course, the internal combustion engine of the presentinvention is preferably a multi-cylinder engine with a plurality ofpistons 13 that are slidably disposed within a corresponding number ofcylinders 12. Moreover, while only one intake valve 17 and one exhaustvalve 19 is shown per cylinder 12, it will be apparent from thisdisclosure that more than one intake valve and more than one exhaustvalve can be used per cylinder in carrying out the present invention.The center O₁ of the crankshafts (not shown in the FIG. 1) is disposedat a position offset on one side from the central axis X of the cylinder12 as seen in FIGS. 3 and 4. Accordingly, as described below, the intakeprocess and the expansion process have greater than 180° of crank angle(CA) allocated thereto. As seen in FIG. 1, an ignition plug 20 isdisposed on an approximate center of the cylinder 12. A fuel injectionvalve 15 is disposed on an intake manifold. The intake valve 17 and theexhaust valve 19 are operatively coupled to the intake valve drivingactuator 16 and the exhaust valve driving actuator 18, respectively,such that the valves 17 and 19 are opened and closed independently. Theintake valve driving actuator 16 and exhaust valve driving actuator 18are preferably electromagnetically operated actuators that havesubstantially the same structures.

[0027] The electromagnetic actuator controller 6 together with theintake valve driving actuator 16 and exhaust valve driving actuator 18form an electromagnetic valve driving device. The electromagnetic valvedriving device of the present invention can be, for example, the onedisclosed in of Japanese Patent Application No. 2000-1453525 (U.S.patent application Ser. No. 09/438,499). The entire disclosures ofJapanese Patent Application No. 2000-1453525 and U.S. patent applicationSer. No. 09/438,499 are hereby incorporated herein by reference,especially with regard to the electromagnetic valve driving devicedisclosed therein. Instead of using the electromagnetic valve drivingdevice, a hydraulic valve driving device such as the one shown in FIG. 9can be used.

[0028] The electromagnetic actuator controller 6, the intake valvedriving actuator 16 and exhaust valve driving actuator 18 areconventional components that are well known in the art. Sinceelectromagnetic actuator controllers, electromagnetic actuators, such aselectromagnetic actuator controller 6, the intake valve driving actuator16 and exhaust valve driving actuator 18, are well known in the art,these structures will not be discussed or illustrated in detail herein.Moreover, the electromagnetic valve driving device forms “valve controlmeans” which as utilized in the claims should include any structure thatcan be utilized to carry out the function of opening and closing thevalves 17 and 19 of an engine in accordance with present invention.

[0029] The intake valves 17 and the exhaust valves 19 are eachmaintained at neutral positions by a pair of springs (not shown) in aconventional manner. The springs are axially aligned with the valves 17and 19, respectively, with each of the valves 17 and 19 being positionedbetween a pair of springs. Also, two electromagnetic coils are disposedon each of the valves 17 and 19. The electromagnetic coils bias thesprings in the opening direction and the closing direction,respectively. Since electrification and stoppage of the electromagneticcoils are controlled by the electromagnetic actuator controller 6, eachof the valves 17 and 19 is opened and closed based on the lift propertyshown in FIG. 2. Since the moving speeds of the valves 17 and 19 aredetermined by the natural frequency of the spring-mass system, themovement of the valves become relatively slow with respect to the crankangle as the mechanism starts high-speed rotation and actual period perunit crank angle becomes shorter. Therefore, in the valve lift propertyrelative to the crank angle, the inclinations of the opening timing andclosing timing vary depending on the rotations of the mechanism.

[0030] As seen in FIG. 1, the aforementioned internal combustion engineincludes a crank angle sensor 11 that outputs a unit crank angle signal,and a cylinder detection sensor 9 that outputs a cylinder detectionsignal. These detection signals are inputted into an the engine controlunit 1, along with other signals such as intake air amount signal,throttle opening signal, and water temperature signal. The enginecontrol unit 1 controls the opening and closing timings of the intakevalves 17 and the exhaust valves 19 through the aforementionedelectromagnetic actuator controller 6, the intake valve driving actuator16 and exhaust valve driving actuator 18 based on these detectionsignals. In one embodiment, the valve driving device closes the intakevalves 17 at a predetermined closure timing that corresponds to at leastone engine operating condition detected from these detection signals sothat the predetermined timing is set before bottom dead center at leastunder the detected engine operating condition. Thus, the valve drivingdevice is controllably arranged to vary and control the closure timingof the intake valves 17 to a target closure timing of the intake valves17 that is determined based on the detected engine operating conditions.The target closure timings of the intake valves 17 include at least onetiming set before bottom dead center. A battery 7 is provided to supplyelectrical power to the electromagnetic actuator controller 6.

[0031] The control unit I preferably includes a microcomputer with acontrol program that controls the electromagnetic actuator controller 6as discussed above. The control unit 1 can also include otherconventional components such as an input interface circuit, an outputinterface circuit, and storage devices such as a ROM (Read Only Memory)device and a RAM (Random Access Memory) device. The control unit 1 isoperatively coupled to the electromagnetic actuator controller 6 in aconventional manner. The internal RAM of the control unit 1 storesstatuses of operational flags and various control data. It will beapparent to those skilled in the art from this disclosure that theprecise structure and algorithms for the control unit 1 can be anycombination of hardware and software that will carry out the functionsof the present invention. In other words, “means plus function” clausesas utilized in the specification and claims should include any structureor hardware and/or algorithm or software that can be utilized to carryout the function of the “means plus function” clause.

[0032] In an early closing Miller cycle internal combustion engine inwhich a Miller cycle operation is achieved by closing the intake valve17 before a bottom dead center position, the crankshaft center O₁ isoffset from a cylinder central axis X, in such a direction that anintake process and an expansion process have greater than 180° crankangle.

[0033] As shown in FIGS. 5 and 6, the situation is illustrated in whichthe center O₁ of the crankshaft is positioned on a cylinder central axisX. In other words, the center O₁ of the crankshaft is aligned with thecentral axis X of the cylinder. This arrangement has a crank offset ofzero (0°) with three basic reference points (i.e., the crankshaft centerO₁, a crankpin center O₂, and a piston pin center O₃). In thisarrangement, the piston pin center O₃ is aligned on the central axis X,at both top dead center (TDC) position as shown in FIG. 5 and the bottomdead center (BDC) position as shown in FIG. 6. Accordingly, the fourprocesses (i.e., intake, compression, expansion, and exhaust) each has180° of crank angle (CA) allocated thereto. In the FIGS. 5 and 6, thelength 1 of a connecting rod and the rotational radius r of the crankpinare shown.

[0034] On the other hand, as shown in FIGS. 3 and 4, when the crankshaftcenter O₁ is offset from the central axis X of the cylinder 12, thebottom dead center position and the top dead center position of thepiston 13 still occur when the three reference points (i.e., thecrankshaft center O₁, the crankpin center O₂, and the piston pin centerO₃) are aligned along a single reference line. At this time, as shown inFIGS. 3 and 4, the connecting rod and the crank arm are inclinedrelative to the central axis X of the cylinder 12. Where the offsetamount of the crankshaft center O₁ from the cylinder center axis X is H,the inclination angle θ_(tdc) at the top dead center position isθtdc=sin⁻¹{H/(r+1)} as shown in FIG. 3. On the other hand, theinclination angle θ_(bdc) at the bottom dead center position isθbdc=sin⁻¹{H/(1−r)} as shown in FIG. 4. Therefore, based on theseequations, the inclination angle θ_(tdc) at the top dead center positionis less than the inclination angle θ_(bdc) at the bottom dead centerposition, i.e., θ_(tdc)<θ_(bdc). If the rotational direction of thecrankshafts is in the direction of the arrowω) in FIGS. 3 and 4, theintake process and the expansion process, during which the piston 13moves from the top dead center position to the bottom dead centerposition in this rotational direction, becomes greater than 180° crankangle, while the compression process and the exhaust process become lessthan 180° crank angle. More specifically, the crank angular range duringwhich the intake process and the expansion process occur is180+(θ_(bdc)-θ_(tdc)), which is greater by (θ_(bdc)-θ_(tdc)) than thecase where there is no crank offset.

[0035] Referring now to FIGS. 7 and 8, valve timing diagrams showexamples of opening/closing timings of the intake valves for the earlyclosing Miller cycle engine. FIG. 7 shows the case where there is nocrank offset, while FIG. 8 shows the case where there is a crank offsetin accordance with the present invention. When there is no crank offset,the intake process and the expansion process both have 180° crank angle,as described above. The intake valve opening timing (IVO) is set atshortly before the intake top dead center, while the intake valveclosing timing (IVC) is set at an angle that is advanced relative to theintake bottom dead center. The effective intake process capacity isdetermined by this intake valve closing timing.

[0036] On the other hand, where there is a crank offset, the intakeprocess becomes longer than 180° crank angle as described above. In FIG.8, the valve timing diagram is drawn with respect to the position of itstop dead center (TDC) in order to make an easy comparison with FIG. 7.In this manner, the range of crank angle that corresponds to the intakeprocess is enlarged. Therefore, when the intake process capacity duringMiller cycle engine is secured in the similar manner as in the case ofFIG. 7, the position of the intake valve closing timing (IVC) relativeto the top dead center (TDC) needs to be at a relatively delayedposition in comparison with the case of FIG. 7. Accordingly, the angularworking range of the intake valve (crank angle between IVO and IVC) isenlarged. Therefore, more flexibility is allowed in the design of thevalve lift curve. Also, when the identical valve working angle is to beobtained, the intake valve closing timing can be set at an angle that issignificantly advanced from the bottom dead center. Accordingly, theintake process capacity can be further decreased during the Miller cycleoperation.

[0037] Next, FIG. 9 shows an example of a structure in which a hydraulicvalve driving device is utilized to drive the intake valves 17 and theexhaust valves 19. Since the intake valves 17 and the exhaust valves 19basically have the same structure, the intake valves 17 and the exhaustvalves 19 are controlled in the same manner. Thus, the hydraulic valvedriving device will only be illustrated as operating a pair of intakevalves 17. The hydraulic valve driving device replaces theelectromagnetic actuator controller 6, the intake valve driving actuator16 and exhaust valve driving actuator 18 of the first embodiment shownin FIG. 1 to open and close the intake valves 17 and the exhaust valves19.

[0038] This hydraulic valve driving device basically includes a reservetank 901, a hydraulic pump 902, a hydraulic adjusting valve 903, anaccumulator 904, a high pressure line 905, a valve opening hydraulicswitching valve 906, a plurality of hydraulic cylinders 907, a valveclosing hydraulic switching valve 911, a plurality of valve springs 909,and a drain line 912. A hydraulic actuator is formed by the valveopening hydraulic switching valve 906, the hydraulic cylinders 907, thevalve closing hydraulic switching valve 911, the valve springs 909. Thevalve opening hydraulic switching valve 906 opens and closes the highpressure line 905, while the valve closing hydraulic switching valve 911opens and closes the drain line 912. In this structure, the hydraulicpump 902 and the accumulator 904 always generate a high hydraulicpressure. As the valve opening hydraulic pressure switching valve 906 isopened while valve closing hydraulic switching valve 911 is closed by acontrol signal from the engine control unit 1 (not shown in the FIG. 9),the hydraulic pressure acts on the hydraulic pressure cylinders 907.Accordingly, the valves 17 open. Then, as the valve opening hydraulicswitching valve 906 is closed while the valve closing hydraulicswitching valve 911 is opened, the hydraulic pressure of the hydrauliccylinders 907 is immediately released. Accordingly, the valves 17 closedue to the spring force of the valve springs 909.

[0039] Thus, each intake valve 17 is preferably driven through anelectromagnetic or hydraulic actuator. By providing either anelectromagnetic or a hydraulic actuator for each intake valves 17 toopen and close the intake valves 17, as disclosed in Japanese Laid-OpenPatent Application H8-189315, the intake valves 17 can be opened/closedat any desired timing. In this manner, an early-closing Miller cycleoperation can be performed easily. In this type of device, the shortestperiod of time in which the valve 17 is open is uniquely determinedbased on the responsiveness of the actuator or the applied voltage,regardless of the rotations of the mechanism. However, in thisinvention, the valve angular working range during the early closingMiller cycle operation is enlarged due to the crank offset. Therefore,even if the actual period of time during which the valve 17 is open isthe same, the early closing Miller cycle operation can be performed in ahigher-speed region. Also, if the maximum rotation speed during theMiller cycle operation is the same, the valve opening period (actualperiod of time) becomes longer because the valve angular working rangeduring the early closing Miller cycle operation is enlarged due to thecrank offset. Therefore, it is possible to utilize, for instance a smallactuator, which does not have high responsiveness, or to decrease theconsumption of electric power. In the case of a hydraulic actuator, theresponsiveness is always determined by the hydraulic pressure.Therefore, the control is possible with lower hydraulic pressure.

[0040] In the early closing Miller cycle internal combustion engineaccording to the present invention, the intake valve closing timing,which is on the advanced angle side relative to the intake bottom deadcenter, can be effectively delayed while maintaining the same intakeprocess capacity. Therefore, if the intake valve opening timing is onthe same position, the requisite valve angular working range isrelatively enlarged. Accordingly, there is more flexibility in design ofvalve lift curve. Also, if restrictions from the valve lift curve of theintake valve are the same, the intake valve closing timing can bepositioned further toward the advance angle side from the bottom deadcenter. Accordingly, the intake process capacity can be furtherdecreased in the Miller cycle operation.

[0041] Particularly, when the Miller cycle engine is combined with theelectromagnetic or hydraulic valve driving device, the operable limit ofthe early closing Miller cycle operation in the high-speed region can beextended to a higher rotation side. The operable limit is set by theshortest open period that is determined by the responsiveness of theactuator. Furthermore, the size of the actuator can be decreased, andthe electric power consumption and/or hydraulic power pressure to besupplied can also be decreased.

[0042] As another embodiment, the intake valves can be driven by amechanical valve driving device that is mechanically driven along with amovement of the crankshaft and this can be achieved by a regularcamshaft having static cam lift property and driven mechanically alongwith a movement of the crankshaft.

[0043] Referring to FIG. 10, the a mechanical valve driving device canfurther include the actuator controller and one or more electromagneticor hydraulic actuators 16 and 18 to control the opening and closingtimings of the intake valves 17 and the exhaust valves 19 based on theaforementioned detection signals. This can be achieved by a regularcamshaft having static cam lift property and changing the phase of theopening and closing timings of the intake valves 17 and the exhaustvalves 19, or a mechanical valve driving device that can change the camlift property continuously or step by step. For instance, U.S. Pat. No.5,988,125 discloses a mechanical valve driving device that cancontinuously change the valve angular working range. The entiredisclosure of U.S. Pat. No. 5,988,125 is hereby incorporated herein byreference, especially with regard to the movable valve mechanismdisclosed therein. Early closing Miller cycle operation can be achievedby combining this type of device and a mechanism that changes the phaseof the center of the angular working range with respect to thecrankshaft, and by advancing the angle of the center of the angularworking range, while narrowing the angular working range. In thisinvention, the valve angular working range is enlarged due to the crankoffset, as described above, when early closing Miller cycle operation isperformed. Therefore, more flexibility is allowed in designs of, forinstance, the cam profile.

[0044] The terms of degree such as “substantially”, “about” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.For example, these terms can be construed as including a deviation of atleast ±5% of the modified term if this deviation would not negate themeaning of the word it modifies.

[0045] This application claims priority to Japanese Patent ApplicationNo. 2000-266725. The entire disclosure of Japanese Patent ApplicationNo. 2000-266725 is hereby incorporated herein by reference.

[0046] While only selected embodiments have been chosen to illustratethe present invention, it will be apparent to those skilled in the artfrom this disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing description of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents. Thus, the scope ofthe invention is not limited to the disclosed embodiments.

What is claimed is:
 1. An early closing Miller cycle internal combustionengine, comprising; a piston slidably disposed in a cylinder toreciprocate along a cylinder central axis; an intake valve disposed inan intake opening of said cylinder to open and close said intakeopening; an exhaust valve disposed in an exhaust opening of saidcylinder to open and close said exhaust opening; a valve driving devicearranged to close said intake valve before bottom dead center to achievethe Miller cycle operation; a crankshaft operatively coupled to saidpiston to move said piston in said cylinder, said crankshaft having acrankshaft center axis of rotation offset from said cylinder centralaxis in such a direction that an intake process and an expansion processhave greater than 180° crank angle.
 2. The early closing Miller cycleinternal combustion engine as set forth in claim 1, wherein said valvedriving device mechanically drives said intake valve by moving alongwith a movement of said crankshaft.
 3. The early closing Miller cycleinternal combustion engine as set forth in claim 1, wherein said valvedriving device includes a hydraulic actuator which hydraulically drivessaid intake valve.
 4. The early closing Miller cycle internal combustionengine as set forth in claim 1, wherein said valve driving deviceincludes an electromagnetic actuator which drives said intake valve. 5.The early closing Miller cycle internal combustion engine as set forthin claim 1, wherein said valve driving device closes said intake valveat a predetermined closure timing that corresponds to a detected engineoperating condition, and said predetermined timing is set before saidbottom dead center at least under said detected engine operatingcondition.
 6. The early closing Miller cycle internal combustion engineas set forth in claim 1, wherein said valve driving device iscontrollably arranged to vary a closure timing of said intake valve,said valve driving device controls said closure timing of said intakevalve to a target closure timing of said intake valve that is determinedbased on a detected engine operating condition, and said target closuretiming of said intake valve includes a timing set before said bottomdead center.
 7. The early closing Miller cycle internal combustionengine as set forth in claim 4, wherein said valve driving device closessaid intake valve at a predetermined closure timing that corresponds toa detected engine operating condition, and said predetermined timing isset before said bottom dead center at least under said detected engineoperating condition.
 8. The early closing Miller cycle internalcombustion engine as set forth in claim 4, wherein said valve drivingdevice is controllably arranged to vary a closure timing of said intakevalve, and controls said closure timing of said intake valve to a targetclosure timing of said intake valve that is determined in accordancewith a detected engine operating condition and said target closuretiming of said intake valve includes a timing set before said bottomdead center.
 9. An early closing Miller cycle internal combustionengine, comprising; a piston slidably disposed in a cylinder toreciprocate along a cylinder central axis; intake valve means foropening and closing an intake opening of said cylinder; an exhaust valvemeans for opening and closing an exhaust opening of said cylinder; valvecontrol means for closing said intake valve before a bottom dead centerto achieve the Miller cycle operation; crank means for moving saidpiston in said cylinder, said crank means having a center crank axisoffset from said cylinder central axis in such a direction that anintake process and an expansion process have greater than 180° crankangle.